Magnetic Disk Track Segmentation for Adaptive Data Refresh
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Solution Overview
Problem
Existing magnetic disk devices face performance deterioration due to unnecessary data refresh caused by uniform counting of writing cycles across varying magnetic film thickness areas, leading to excessive refresh operations and data readability issues.
Innovation Solution
The magnetic disk device divides tracks into multiple areas based on adjacent track interference characteristics, applying weights and using separate counters for each area to determine the frequency of refresh, thereby optimizing the refresh process and reducing unnecessary operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uniform writing cycle counting is applied across all areas of a track, then the implementation is simple, but refresh operations occur more than necessary leading to performance deterioration
Solution Approach 1:
The track is divided into multiple divided areas along the circumferential direction, with each area having its own counter and threshold value. This segmentation allows the system to apply different refresh strategies to different areas based on their specific adjacent track interference characteristics, thereby reducing unnecessary refresh operations while maintaining data integrity.
Solution Approach 2:
Each divided area is assigned different characteristics including area identification information, counter threshold values, and weights based on its specific adjacent track interference properties. This local differentiation enables optimized refresh control for each area, improving overall device performance by avoiding uniform over-refreshing.
2Reliability
If refresh is performed based on uniform writing cycle threshold, then data readability is maintained, but unnecessary refresh operations increase frequency
Solution Approach 1:
By segmenting the track into multiple divided areas with separate counters and threshold values, the system can perform refresh operations only when necessary for each specific area, thereby maintaining data readability while reducing the overall frequency of unnecessary refresh operations.
Solution Approach 2:
Different threshold values and weights are assigned to different divided areas based on their adjacent track interference characteristics. This parameter differentiation allows the system to adapt refresh timing to actual data degradation risks, performing refresh only when needed for each area rather than applying a uniform threshold.
3Productivity
If weighted counting with multiple counters per track is implemented, then refresh frequency is optimized, but the system complexity increases
Solution Approach 1:
The track is divided into multiple divided areas, each with its own counter and threshold value stored in storage units. This segmentation organizes the complexity into manageable, independent units that can be controlled separately, improving refresh efficiency while keeping the system structure systematic and maintainable.
Solution Approach 2:
The controller is designed to universally handle multiple counters and threshold values through a unified control mechanism that processes area identification information, selects appropriate thresholds, and manages weighted counting. This multi-functionality allows optimized refresh control across all divided areas without proportionally increasing control complexity.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a memory and a controller. The memory stores, for a predetermined track on a magnetic disk in the device, a counter, a counter threshold, and weights. The weights are individually set for divided areas of the predetermined track. The weights each have magnitude inversely proportional to a guaranteed number of times of data readout. When writing to an adjacent track of one or more of the divided areas is executed, the controller multiplies a number of times of writing by the weight corresponding to the one or more of the divided areas and adds the number of times of writing to the counter. When a numerical value of the counter reaches the counter threshold, the controller executes refresh to rewrite data in the predetermined track or executes reading for determining whether or not to perform the refresh.